Forging machine



Sept. 5, O, H L 3,339,397

FORGING MACHINE Filed May 25, 1965 IgyguTDN,

OTRHAR HEIHL Aft- United States Patent 3,339,397 FORGING MACHINE Othmar Heimel, Behamberg, Austria, assignor to Gesellschaft fur Fertigungstechnik und Maschinenbau Gesellschaft m.b.H., Steyr, Austria Filed May 25, 1965, Ser. No. 458,662 Claims priority, application Austria, July 23, 1964,

A 6,323/ 64 9 Claims. (Cl. 72-407) Various types of forging machines are known, which comprise pairs of oppositely moving hammers blowing onto the workpiece, which is introduced between the hammers. In most cases, the hammers are strictly mechanically driven, e.g., the hammers consist of connecting rods, which are driven with the aid of eccentric shafts. As the number of blows per unit of time performed by such mechanically driven hammers cannot be indefinitely increased, for design reasons, the shaping speeds are relatively restricted. This has the disadvantage that various workpieces or workpieces of various materials cannot be deformed or forged or their deformation or forging is difiicult.

It is also known to drive hammers by compressed gas and to return the hammer by applying hydraulic pressure from the opposite end, while compressing the gas, whereas a mechanical drive for the hammers is eliminated. This results in very high blowing and shaping rates so that the workpiece can be subjected to shaping with high energy, as is particularly desirable in die forging. Considerable difiiculties have previously arisen when the machines should operate in accordance with the counterblow principle, with pairs of hammers which are directed against each other and blow against each other, and when the machines should be controlled so that the two hammers of each pair blow exactly in synchronism, their blowing movements being performed simultaneously and at the same rates.

It is an object of the invention to provide such a forging machine, in which a synchronous hammer movement is ensured in spite of the fact that the hammers are driven by compressed gas.

Based on a forging machine in which the hammers are arranged in pairs and the hammers of each pair blow against each other and the workpiece, which is introduced between them, and are adapted to be driven in the blowing direction by compressed gas and to be hydraulically returned to their initial position with the aid of cylinder-piston units, the invention resides essentially in that a common driving piston, which is displaceable in a gas accumulator, is provided for each pair of hammers, and at its end remote from the gas accumulator has two piston faces, which are adapted to be supplied with hydraulic pressure and arranged in a cylindrical chamber and an annular cylindrical chamber, which chambers are separate from each other and connected by hydraulic transmission conduits to the two cylinder-piston units, which are identical. So far, a separate driving piston adapted to be supplied with compressed gas was used for each hammer, so that it was difficult to obtain a synchronous movement of the hammers when working on the counterblow principle. Now each pair of hammers has a common driving piston. It is obvious that this driving piston cannot act directly on the two hammers. For this reason a hydraulic transmission of the movement of the driving piston to the two pistons of the cylinder-piston units is provided. Owing to the equality of the size of the two driving piston faces to be supplied with liquid under pressure and owing to the equality of the significant portions of the cylinder-piston units, equal rates of liquid are being fed in both transmission systems so that the hammers must move equal distances. The simultaneousness of the movements of both hammers is inherently ensured in that these movements are initiated by or derived from the common driving piston. If one of the hammers presents a greater resistance to its movement, e.g., owing to different friction conditions, this resistance will result in a pressure differential rather than in a displacement differential in the two transmission systems. Displacement differentials could only result from different compressions of the two hydraulic columns and different leakage losses during the blow. As the compressibility of liquids is very low and differences between the leakage losses cannot arise to a significant extent in the extremely small blow times, the synchronism of the two hammers is ensured except for practicallyinsignificant values. A mechanical transmission of the movement of the driving piston would be impossible for design reasons at the blowing speeds of 15 meters per second which may arise.

The return movement of the driving piston to its initial position with simultaneous compression of gas could be efiected by means of the cylinder-piston units associated with the hammers when these units are hydraulically returned. This would involve the danger, however, that any vibration of the hydraulic column in the transmission conduits would cause further hammer blows. Such double blows are not desirable during die forging. In a development of the invention, the transmission conduits consist of two sections, which can be shut off from each other, and that section which is adjacent to the driving piston is adapted to be connected to a pump and the conduit section which is adjacent to the cylinder-piston unit is adapted to be connected through a biased valve to the exhaust when the sections are shut off from each other. Thus, the hydraulic column is immediately interrupted when the hammer blow has been performed so that vibrations are also suppressed and there is no danger of double blows. At the same time, the conduit section adjacent to the driving piston is connected to a pump so that the driving piston can be returned to its initial position and the gas can be compressed in spite of the interruption of the conduit. Duing the following return movement of the dies, the liquid from the conduit section adjacent to the cylinder-piston unit may be displaced into the exhaust. The biased valve has the advantage that the rebounding of the hammers gives rise to a build-up of pressure in the respective conduit section and this build-up of pressure brakes the rebounding movement. This pressure can be reduced to the desired value by an adjustment of the bias of the valve.

According to the invention, a control valve is provided, which is common to both transmission conduits and serves for shutting off the conduit sections and for connecting them to the pump and exhaust. This control valve is urged by a compression spring to its blocking and diverting position whereas it is adapted to be displaced to its open position against the spring force by pressure liquid supplied through a pilot conduit. Under the action of the spring acting on this control valve, the latter is normally in a position in which the transmission conduit sections adjacent to the driving piston are connected to the pump and those sections which are adjacent to the cylinderpiston units are connected to the exhaust. As a result, the driving piston and the hammers as well as the cylinder-piston units are in their initial position. If liquid pressure acting against the spring force is then applied to the control valve, the latter will be displaced to its open position. This means that the flow through the transmission conduits is permitted soon after the connections to the pump and exhaust have been blocked. Upon release, the gas can expand and the movement of the driving piston is hydraulically transmitted to the cylinder-piston units associated with the hammers.

The pilot conduit for the control valve which has been described includes a pilot valve, which is coupled to the driving piston. At the end of the gas expansion stroke of the driving piston, this pilot valve acts to interrupt the supply of pressure liquid to the pilot conduit and to connect that section of this conduit which leads to the control valve to the exhaust. As soon as the supply of pressure liquid to the control valve is discontinued, the spring becomes effective and urges the valve to its closed position. As the pilot valve is coupled to the driving piston, the control valve is automatically moved at the end of the expansion stroke to the position in which the transmission conducts are blocked, one section of each of these conduits is connected to the pump and the other section of each of these conduits is connected to the exhaust so that the driving piston and the pistons of the cylinderpiston units are returned to their initial position.

In a development of the invention, the pilot conduit incorporates a pre-control valve, which precedes the pilot valve in the direction of fiow in which pressure liquid is supplied, which pre-control valve is hydraulically reciprocable with the aid of a solenoid valve and in its two end positions connects exhaust to that pilot conduit section which leads to the pilot valve and control valve whereas the pre-control valve permits of a flow through it only when it passes through its intermediate position. As the pre-control valve connects in its two end positions the pilot conduit to the exhaust, the control valve will not be supplied with pressure liquid and shifted at an inappropriate time before the pistons have returned to their initial position. The control valve can be displaced to change its connections only in the intermediate position of the pre-control valve. The movement of the pre-control valve is relatively slow in order to enable a suflicient flow of pressure liquid through it during its movement. Besides, the pre-control valve has the advantage of enabling always the same control operation, irrespective of its respective end position. This results in a simpler design.

Those cylinder chambers of the cylinder-piston units which face the hammers are connected to a pressure liquid conduit, which is connected in turn to a pressure liquid accumulator. Thus, the liquid from these cylinder chambers can escape into the accumulators during the hammer blow. On the other hand, the pistons of the cylinder-piston units can be returned rapidly to their initial position when the hammer blow has been performed without need for the pump to supply the full amount of liquid required for this purpose.

The accompanying drawing is a diagrammatic view showing by way of example an embodiment of a forging machine according to the invention. For a clearer showing, the driving piston and its control means are shown on a larger scale than the remaining members of the machine.

Two hammers I blow against each other or a workpiece Which has been introduced between them and are pivoted to the pistons 2 of cylinder-piston units 2, 3. Those cylinder chambers of the cylinder-piston units 2, 3 which face the hammers 1 are connected by pressure liquid conduits 4 to pressure liquid accumulators 5. Application of pressure to the pistons 2 through the conduit 4 causes the hammers 1 to be moved to and held in their initial position shown on the drawing. It will be understood that the machine may be provided with at least one similar pair of hammers, which is offset 90.

A common driving piston 6 is provided for driving the two hammers 1 in the blowing direction. This driving piston is adapted to be displaced in a gas accumulator 7, which is filled with nitrogen. At its end remote from the gas accumulator 7, the piston 6 has two piston faces 8, 9, which are of equal size and disposed in a cylindrical chamber 10 and an annular cylindrical chamber 11, which is separate from chamber 10. These faces are adapted to be supplied with pressure liquid. Conduits 12, 13 and 14, 15 lead from the chambers 10, 11 to the cylinders 3 of the cylinder-piston units 2, 3. A control spool valve 16 is held by a spring 17 in the blocking position, which is shown. In this position, the sections 12, 13 and 14, 15 of the transmission conduits leading from the driving piston to the cylinder-piston units are shut off from each other and the sections 12, 14, which are adjacent to the driving piston, are connected by a conduit 18 to a pump, which is not shown, whereas those conduit sections 13, 15 which are adjacent to the cylinder-piston units are connected by the conduit 19 and a biased valve 20 to the exhaust 21. The pressure liquid from the conduit 18 maintains the driving piston 6 in its initial position shown, in which the gas in the accumulator 7 is compressed.

A pilot conduit 22, 23 is provided for moving the control spool valve 16 against the force of the spring 17 acting on this valve. The conduit 22, 23 incorporates a pilot spool valve 24, which is connected to the driving piston 6. The pilot conduit incorporates further a pre-control slide valve 25, which is reciprocable with the aid of a solenoid slide valve 26. In the position shown on the drawing, the pilot conduit 22, 23 is connected to the exhaust 21' so that the spring 17 is fully effective. When the solenoid valve 26 is adjusted, pressure liquid flows from the conduit 27 to the right-hand end of the pre-control valve 25, which is now displaced to the left and in its intermediate position permits pressure liquid from the conduit 23a to flow through the valve 25. Pressure liquid flows thus through the pilot valve 24 and the pilot conduit section 22 to the pilot valve 16, which is now displaced to the right against the force of the spring 17.

During this displacement, the conduit 18 is initially interrupted and the conduit 19 to the exhaust is blocked. Then the conduit sections 12, 13 and 14, 15 are connected so that the driving piston 6 can perform its expansion stroke. The movement of this piston is now transmitted by the transmission conduits 12, 13 and 14, 15 to the pistons 2 of the cylinder-piston units 2, 3 so that the hammers 1 are forced toward each other. Shortly before the driving piston 6 has terminated its expansion stroke, the pilot valve 24 has interrupted the pilot conduit 22, 23 and the conduit section 22 leading to the control valve 16 has been connected by the pilot valve 24 through the conduits 28 and 19 and the biased valve 20 to the exhaust 21 so that the spring 17 can urge the control valve 16 back to its blocking or diverting position shown on the drawing. In this position, the conduit sections 12, 14 are connected to the supply conduit 18 from the pump and the conduit sections 13, 15 are connected to the exhaust 21. The driving piston 6 returns to its initial position and compresses the gas. Under the action of pressure liquid supplied from the conduit 4 and the pressure accumulators 5, the pistons 2 and with them the hammers 1 are returned to their initial position while liquid is displaced from the conduit sections 13, 15. The precontrol valve 25 has now reached its left-hand end position, in which the conduit section 23 is connected to exhaust 21'. A repetition of the cycle which has been described can be initiated by an operation of the solenoid valve 26.

To make up for gas losses from the gas accumulator 7, the latter may be connected by a solenoid valve, not shown, and suitable conduits to a gas container under higher pressure. Similarly, the desired charge pressure may be adjusted by an interposed reducing valve. By a variation of the charge pressure, the blow energy of the hammers may then be varied in a linear relation. Finally, the switching speed of the pre-control valve 25 may be controlled with the aid of a throttle valve, which is not shown.

What I claim is:

1. A forging machine, which comprises at least one pair of hammers and drive means for reciprocating the hammers of said pair in mutually opposite directions toward each other and away from each other, said drive means comprising two identical cylinder-piston units, each of which is associated with one hammer of said pair, a gas accumulator, a driving piston slidably fitted in said gas accumulator, said driving piston having at its end opposite to said gas accumulator two piston faces of equal size, cylinder means in which said piston is slidably mounted and which define with said piston an annular cylindrical working chamber adjoiningone of said piston faces and a cylindrical working chamber adjoining the other of said piston faces and separate from said annular cylindrical working chamber, and two hydraulic transmission conduits, each of which connects one of said working chambers to one of said cylinder-piston units.

2. A forging machine as set forth in claim 1, in which said cylinder means comprise an inner cylinder and an outer cylinder spaced around said inner cylinder, and said piston has an annular skirt slidably fitted between said outer and inner cylinders and formed with said one end face, said skirt defining with said other piston face and said inner cylinder said cylindri-cal working chamber.

3. A forging machine as set forth in claim 1, in which each of said transmission conduits incorporates blocking valve means normally separating said conduit into a first conduit section communicating with said driving piston and a second conduit section communicating with one of said cylinder piston units, said machine further comprising a liquid pressure source, an exhaust, biased valve means, connected to said exhaust, and diverting Valve means normally connecting said first conduit sections to said liquid pressure source and said second conduit sections through said biased valve means to said exhaust, and means for operating said blocking and diverting valve means to disconnect said liquid pressure source and exhaust from said first and second conduit sections and to connect said first and second sections of each of said transmission conduits to each other.

4. A forging machine as set forth in claim 3, in which said blocking valve means and diverting valve means associated with both transmission conduits are incorporated in a common control valve, and which comprises spring means tending to reset said blocking and diverting valve means, and a pilot conduit connected to said control Valve for supplying liquid pressure thereto to operate said blocking valve means and diverting valve means against the action of said spring means.

5. A forging machine as set forth in claim 4, in which said liquid pressure source comprises a pump.

6. A forging machine as set forth in claim 4, which comprises a pilot valve incorporated in said pilot conduit and coupled to said driving piston, said pilot valve being arranged to block said pilot conduit and to connect said pilot conduit between said pilot valve and said control valve to said exhaust when said driving piston is in its end position remote from said gas accumulator.

7. A forging machine as set forth in claim 6, which comprises a pre-control valve incorporated in said pilot conduit on the side of said pilot valve opposite to said control valve and a solenoid valve operable to reciprocate said pro-control valve between two end positions through an intermediate position, said pre-control valve being adapted to connect in each of said end positions said pilot conduit between said pre-control valve and said pilot valve to said exhaust, and to connect in said intermediate position said pilot conduit on both sides of said pre-control valve.

8. A forging machine as set forth in claim 1, in which each of said cylinder-piston units comprises a working chamber adjacent to the associated hammer and which comprises pressure liquid accumulator means and pressure liquid conduits connecting said pressure liquid accumulator means to said working chambers of said cylinder-piston units.

9. A forging machine as set forth in claim 8, in which said pressure liquid accumulator means comprise two pressure accumulators, each of which is connected to one of said liquid pressure conduits.

References Cited UNITED STATES PATENTS 2,545,570 3/1951 Caldwell 72-55 2,615,306 10/1952 Alcorn 72-20 2,729,943 l/ 6 Clarke 72-407 2,742,802 4/ 1956 Clarke 72-4 2,926,497 3 1960 Biernath 72-23 CHARLES W. LANHAM, Primary Examiner. G. P. CROSBY, Assistant Examiner. 

1. A FORGING MACHINE, WHICH COMPRISES AT LEAST ONE PAIR OF HAMMERS AND DRIVE MEANS FOR RECIPROCATING THE HAMMERS OF SAID PAIR IN MUTUALLY OPPOSITE DIRECTIONS TOWARD EACH OTHER AND AWAY FROM EACH OTHER, SAID DRIVE MEANS COMPRISING TWO IDENTICAL CYLINDER-PISTON UNITS, EACH OF WHICH IS ASSOCIATED WITH ONE HAMMER OF SAID PAIR, A GAS ACCUMULATOR, A DRIVING PISTON SLIDABLY FITTED IN SAID GAS ACCUMULATOR, SAID DRIVING PISTON HAVING AT ITS END OPPOSITE TO SAID GAS ACCUMULATOR TWO PISTON FACES OF EQUAL SIZE, CYLINDER MEANS IN WHICH SAID PISTON IS SLIDABLY MOUNTED AND WHICH DEFINE WITH SAID PISTON AN ANNULAR CYLINDRICAL WORKING CHAMBER ADJOINING ONE OF SAID PISTON FACES AND A CYLINDRICAL WORKING CHAMBER ADJOINING THE OTHER OF SAID PISTON FACES AND SEPARATE FROM SAID ANNULAR CYLINDRICAL WORKING CHAMBER, AND TWO HYDRAULIC TRANSMISSION CONDUITS, EACH OF WHICH CONNECTS ONE OF SAID WORKING CHAMBERS TO ONE OF SAID CYLINDER-PISTON UNITS. 